Researchers have found that heavier babies are more likely to suffer childhood food allergies or eczema.

For the study, published in the Journal of Allergy and Clinical Immunology, the research team carried out a systematic review assessing past studies in humans. After screening more than 15,000 studies, they identified 42 that included data on more than two million allergy sufferers. "We analysed the associations between birth weight, corrected for gestational age, and the incidence of allergic diseases in children and adults," said Kathy Gatford from the University of Adelaide in Australia.

"For each kilogram increase in birth weight there was a 44 per cent increase in the risk that a child had food allergies or a 17 per cent increase in the risk that they had eczema," Gatford said. According to the researchers, they analysed studies that included over 2.1 million people affected by allergic dermatitis, commonly known as eczema, nearly 70,000 people affected by food allergies and over 100,000 people with allergic rhinitis or hay fever. Most of the studies were in children from developed countries and most were European.

"Allergic diseases including eczema, hay fever, food allergies, anaphylaxis and asthma are estimated to affect 30-40 per cent of the world's population," Gatford said. "It is increasingly clear that genetics alone do not explain risks of developing allergies, and that environmental exposures before and around birth can programme individuals to increased or decreased risk of allergies," Gatford added. Most of the allergies in these studies were assessed in young children.